While no one can be sure if H5N1 will be the next pandemic, experts do agree that another pandemic is inevitable. Flu viruses are constantly changing and adapting, so it is very likely that viruses different from the ordinary flu strains will emerge, causing a pandemic. Experts are saying the world is overdue for a pandemic (the last one occurred in 1968), and H5N1 has a real chance of fulfilling their predictions.

Scientists cannot predict whether an avian influenza (H5N1) virus will cause a pandemic. That is why we are focusing on comprehensive public health efforts — increasing surveillance monitoring for outbreaks, international cooperation, antiviral and vaccine stockpiles and building more robust capacity for vaccine production — that will help protect us no matter what pandemic strain emerges or where.

The H5N1 virus can improve its ability to infect humans when "reassortment" occurs, resulting in a new virus with enhanced human transmissibility. This is caused by an exchange of genetic material between human and avian influenza viruses when a human becomes infected with both at the same time. Pigs may also serve as "mixing vessels" for this exchange and then transmit the new virus to humans. Such an event would be announced by a sudden surge of cases with explosive spread.

Three pandemics have occurred in the last 90 years, in 1918, 1957 and 1968. Scientists predict that another pandemic will happen, although they can't say exactly when. The Department of Health and Human Services (DHHS) has compiled a summary of the pandemics and "pandemic scares" that have occurred in the last 100 years.

During a pandemic you're more likely to catch it than seasonal flu because it spreads rapidly and very few people will have immunity. Everyone will be at risk. Some groups of people may be more at risk than others, but every pandemic is different, so until the virus starts spreading it is very difficult to predict who these groups might be.

The virus can improve its transmissibility among humans via two principal mechanisms. The first is a â??reassortmentâ?? event, in which genetic material is exchanged between human and avian viruses during co-infection of a human or pig. Reassortment could result in a fully transmissible pandemic virus, announced by a sudden surge of cases with explosive spread.

Providing leadership to the National Pandemic Influenza Preparedness and Response Task Force, created in May 2005 by the Secretary of the U.S. Department of Health and Human Services. Working with the Association of Public Health Laboratories on training workshops for state laboratories on the use of special laboratory (molecular) techniques to identify H5 viruses. Working with the Council of State and Territorial Epidemiologists and others to help states with their pandemic planning efforts.

No. The current outbreak of H5N1 bird flu is a disease of birds that has made some people sick, but it is not a human pandemic. Bird flu would have to change form (mutate) to become pandemic flu. We don't know if that will ever happen.

Although scientists cannot predict the specific consequences of an influenza pandemic, it is likely that many age groups would be seriously affected. Factors to consider include the following: influenza pandemic could temporarily disrupt activities important to overall public health, the economy, and essential community services.

It is not known. In the 20th century, severe pandemics occurred in 1918 ("Spanish Flu"), 1957 ("Asian Flu") and 1968 ("Hong Kong Flu").

Flu viruses are constantly changing and adapting, so it is likely that viruses sufficiently different from 'ordinary' flu strains to cause a pandemic will emerge from time to time. International disease experts are saying that the world is overdue for the next pandemic. Experts are particularly concerned that the H5N1 virus, which has already caused disease and death in humans, may develop the capacity to pass easilly between people.

The World Health Organization, Centers for Disease Control and Prevention, the Nebraska Health & Human Services System and local health departments are watching for the first signs of an emerging pandemic. In 1918, pandemic flu spread across the country in less than a month. Now, in the era of international air travel, experts say a pandemic will probably spread even faster. As a result:

Migratory birds usually travel the same routes in their annual migrations. In the Northern Hemisphere, birds begin moving south during August and September of each year. North American migratory birds that over-winter in Asia may come into contact with potentially infected domestic or wild birds during the winter months. In spring, migratory birds will migrate north to their breeding grounds in eastern Russia, Alaska, and Canada.

Although H5N1 probably poses the greatest current pandemic threat, other avian influenzas have also infected people in recent years. For example, in 1999, human H9N2 infections were identified in Hong Kong; in 2002 and 2003, human H7N7 infections occurred in the Netherlands and human H7N3 infections occurred in Canada. These viruses also have the potential to give rise to the next pandemic.

Scientists cannot predict whether the H5N1 avian influenza virus will cause a pandemic. But federal, state and local health officials are working with their counterparts throughout the world to track H5N1 as it occurs in birds, and to watch for possible human cases.

From past experience, around 15 to 35 per cent of the population is likely to develop influenza, although it could be more.

These drugs must be started within the first 48 hours of infection in order to help shorten the duration and lessen the severity of disease. Individual flu strains can mutate and become resistant to the drugs. The Centers for Disease Control (CDC) analysis of the H5N1 strains from Asia have shown resistance to amantadine and rimantadine. This means that if the current H5N1 avian flu causes a pandemic, only oseltamivir and zanamivir can be used to treat it.

I think it's important to recognize that any pandemic is a serious event. We are most worried right now about H5N1 because it's been killing half of the people it infects. But, we don't know that the next pandemic ? and there will be another pandemic, the nature of the virus virtually guarantees it ? we don't know if it'll come tomorrow, or if it'll come in 20 years.

Although H5N1 probably poses the greatest current pandemic threat, other avian influenzas have also infected people in recent years. For example, in 1999, human H9N2 infections were identified in Hong Kong; in 2002 and 2003, human H7N7 infections occurred in the Netherlands and human H7N3 infections occurred in Canada. These viruses also have the potential to give rise to the next pandemic.

Influenza viruses are constantly changing over time. The H5N1 virus could become a pandemic strain in one of two ways: 1) it could exchange genetic material from a human flu virus and acquire the ability to easily transmit between people; or 2) it could mutate over time and adapt to human cells. This second process would likely happen over the course of several years.